fix(client): New folder did nothing — prompt() throws in the desktop client

The same `static/` tree is the web page and the application, and Electron does
not implement `window.prompt`: Chromium leaves it to the embedder and Electron
declines. It does not return null — it **throws**. The call sat above its own
try, so clicking produced no folder, no error and nothing on screen to react
to. A dead button, which is exactly how it was reported.

Measured against this repo's own Electron 44 rather than assumed, because the
first two diagnoses this session were reasoned and wrong:

    prompt('name?')  ->  Error: prompt() is not supported.
    confirm('sure?') ->  opens a real modal
    alert('hi')      ->  opens a real modal

So `confirm` and `alert` stay — a dozen call sites depend on them — and only
`prompt` is banned. `test_no_prompt_in_the_spa.py` holds the whole tree to it,
with the near-misses it must not flag (`mkdir_prompt`, `promptForName`).

The name now comes from a field in the toolbar, which works in both clients and
can show the node's refusal beside the input instead of after a dialog has
closed. Navigating away drops a half-typed name: it would otherwise create the
folder somewhere the person is no longer looking.

The rest of the chain was verified end to end and was sound: `dir_create`
{dir,name} → the node's handler → `dir_create_ack`, and `list_dirs` walks the
filesystem rather than the index, so a folder with nothing in it appears on the
very fetch that follows. The field itself was then driven inside a real
Electron window — typing, Enter, the click, and the icon rendering.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011pvMdvLBG92jyhvD5pD6us

1 files changed, 58 insertions, 7 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/static/files-app.js b/packages/meshbay-hub/src/meshbay_hub/static/files-app.js
index fb57a0f..4947f8c 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/files-app.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/files-app.js
@@ -104,19 +104,47 @@ function FilesPanel({
     }
   }, [applyIndex, currentPath]);
 
-  const makeDirectory = useCallback(async () => {
+  // `null` while not creating one; a draft string while the field is open.
+  const [newDirName, setNewDirName] = useState(null);
+  const [creatingDir, setCreatingDir] = useState(false);
+
+  /**
+   * Create a folder in the directory being browsed.
+   *
+   * The name comes from a field in the toolbar rather than `window.prompt`,
+   * which **throws** in Electron — "prompt() is not supported" — and threw
+   * outside this function's try, so clicking the button did nothing at all:
+   * no folder, no error, nothing in the interface to react to. `confirm()` and
+   * `alert()` do work there and are used elsewhere; `prompt` is the one
+   * Chromium leaves to the embedder and Electron declines to implement.
+   *
+   * An inline field is better anyway — it can show the refusal next to the
+   * input instead of after the dialog has closed.
+   */
+  useEffect(() => { setNewDirName(null); }, [currentPath]);
+
+  const makeDirectory = useCallback(async (rawName) => {
     const transport = transportRef.current;
-    if (!transport || !transport.connected) return;
-    const name = prompt(t('group.mkdir_prompt'));
-    if (!name || !name.trim()) return;
+    const name = (rawName || '').trim();
+    if (!name) return;
+    if (!transport || !transport.connected) {
+      setError(t('group.mkdir_offline'));
+      return;
+    }
+    setCreatingDir(true);
     try {
-      await transport.createDirectory(currentPath, name.trim());
+      await transport.createDirectory(currentPath, name);
+      // `list_dirs` walks the filesystem rather than the index, so a folder
+      // with nothing in it is here on this very fetch.
       const indexMsg = await transport.fetchIndex();
       if (indexMsg.entries) setEntries(indexMsg.entries);
       if (indexMsg.dirs) setNodeDirs(indexMsg.dirs);
       if (indexMsg.roots) setNodeRoots(indexMsg.roots);
+      setNewDirName(null);
     } catch (err) {
       setError(err.message);
+    } finally {
+      setCreatingDir(false);
     }
   }, [currentPath]);
 
@@ -374,12 +402,35 @@ function FilesPanel({
                 width a breadcrumb trail needs. The name lives in the tooltip
                 and in aria-label, so it is not lost to anyone reading with
                 something other than their eyes. */''}
-          ${canCreateDir && html`
-          <button class="tb-btn tb-btn-icon" onClick=${makeDirectory}
+          ${canCreateDir && newDirName === null && html`
+          <button class="tb-btn tb-btn-icon" onClick=${() => setNewDirName('')}
             title=${t('group.mkdir')} aria-label=${t('group.mkdir')}>
             <${Icon} name="folder-plus" />
           </button>
           `}
+          ${canCreateDir && newDirName !== null && html`
+          <span class="tb-mkdir">
+            <input type="text" class="tb-mkdir-input" autofocus
+              value=${newDirName} disabled=${creatingDir}
+              placeholder=${t('group.mkdir_prompt')}
+              aria-label=${t('group.mkdir')}
+              onInput=${(e) => setNewDirName(e.target.value)}
+              onKeyDown=${(e) => {
+                if (e.key === 'Enter') makeDirectory(newDirName);
+                if (e.key === 'Escape') setNewDirName(null);
+              }} />
+            <button class="tb-btn tb-btn-icon" title=${t('group.mkdir')}
+              disabled=${creatingDir || !newDirName.trim()}
+              onClick=${() => makeDirectory(newDirName)}>
+              <${Icon} name="check" />
+            </button>
+            <button class="tb-btn tb-btn-icon" title=${t('settings.cancel')}
+              disabled=${creatingDir}
+              onClick=${() => setNewDirName(null)}>
+              <${Icon} name="close" />
+            </button>
+          </span>
+          `}
         </div>
 
         <div class="breadcrumbs">